The present invention relates to a developing device for use in an electrophotographic image forming apparatus.
Developing devices applicable to a copier, facsimile apparatus, laser printer or similar image forming apparatus include one having a developing roller for depositing a toner fed by a toner supply roller on a photoconductive element, and an intermediate developing member interposed between the developing roller and the photoconductive element. The intermediate developing member is implemented as a belt or a roller. In a laser printer, for example, using this type of developing device, the portion of the photoconductive element extending between a charger and the developing device is not charged at the beginning of a printing operation for the first sheet. As a result, a toner deposits on the undesired portion of the photoconductive element to form a black solid smear.
With an image forming apparatus of the type having a semiconductor laser in optics thereof, it has been customary to effect output control, generally referred to as APC, in order to prevent the output of the laser from changing with a change in the temperature of the semiconductor. Specifically, the laser is caused to emit a beam during the interval between consecutive pages. The output of the laser is fed back to control a current to flow through the laser. This brings about a problem that the photoconductive element is exposed during the interval between pages, also causing the toner to deposit thereon in a black solid smear.
In any case, the toner deposited on the unexpected portion of the photoconductive element aggravates toner consumption. Moreover, since most of this part of the toner is collected by a cleaning unit, it increases the amount of waste toner. In addition, such toner is apt to be scattered around in the image forming apparatus.